MARTIAL HEARTS: The glam marriage of Nicolas Sarkozy and Carla Bruni is reportedly in trouble, with stories that she's shacking up with pop star Benjamin Biolay and he's tomcatting with karate champ and political ally Chantal Jouanno. Photo: Reuters

Marital infidelity may be de rigueur in France, but even the most blasé Parisians are transfixed by the scandal du jour — a soap opera starring the country’s president, a karate champ who’s reportedly his girlfriend, his mega-glamorous wife and her pop-star pal.

In the latest episode, President Nicolas Sarkozy sent a plane halfway around the world to bring back first lady Carla Bruni, a supermodel-turned-singer, from Thailand, where she’d been vacationing with her reported squeeze, pop star Benjamin Biolay.

She’s back in Paris, but instead of her digs in the Elysée Palace, she’s sharing a pied-à-terre with Biolay, according to reports.

Bruni’s sojourn with Biolay, who had helped her with her third album, was “shortened by Nicolas Sarkozy” when he “chartered a plane to bring his wife back to Paris,” said Switzerland’s Tribune de Geneve.

Meanwhile, Sarkozy has reportedly found solace in the arms of Chantal Jouanno, a 13-time French karate champion whose moves he admires so much that he appointed her ecology minister.

At 55, Sarkozy is the oldest member of the cast. Bruni is 42, Jouanno 40 and Biolay 36.

Officially, there is “absolutely no comment” from the dashing president. But his office acknowledged that the first lady “will not be traveling to Britain” when Sarkozy visits the country today.

Jouanno’s spokesman said she was “scandalized by this rumor” and threatened to sue over the “slanderous comments.”

Bruni, however, didn’t sound too optimistic about the future of her marriage. An interviewer with Britain’s Sky News TV asked her, “If Nicolas Sarkozy is a keeper, as we say in the UK, is he for keeps? Is he forever?”

She took a long pause.

“I guess marriage should be forever. But who knows what happens,” she said. “I wish it was forever; that’s my hope . . . but we could be dead tomorrow.”

Bruni, an Italian-born heiress whose earlier lovers include Mick Jagger and Eric Clapton, married Sarkozy in February 2008 after a whirlwind three-month romance that enthralled the French.

That was shortly after he divorced his second wife, also a former fashion model. He’d allegedly started an affair with Bruni while married to wife No. 1.

“Do you trust him?” the Sky News interviewer asked Bruni, adding, “I mean, the rumors are that he had many affairs.”

Bruni shot back a piercing stare as she replied, “Oh, yes, very much. He would never have affairs.”

Then she coyly asked, “Have you ever seen a picture of him having an affair?”

Bruni, an aspiring actress who has said she’ll appear in a Woody Allen movie being filmed this year, seemed comfortable playing the role of loyal wife.

Asked if marrying one of the world’s most powerful men was a fairy-tale experience, she said, “The real fairy tale is how lucky, how incredibly lucky, it was for me to fall in love at 40 years and meeting someone I could marry.”

The growing scandal comes at an inconvenient moment for Sarkozy, whose political prospects have been plummeting and whose party faces a potential rout in regional elections that begin Sunday. One of the star candidates of Sarkozy’s UMP party is Jouanno.

The French media, laboring under strict privacy laws, have handled the latest liaisons dangereuses delicately.

After Le Journal du Dimanche helped launch the latest furor — by reporting on its Web site that “Carla Bruni is in love with Benjamin Biolay and the president has found solace with Chantal Jouanno” — the story was taken down due to what the site called its “seriously prejudicial nature.”

Sarkozy is believed to have friends among the paper’s owners.

The satirical publication Le Canard lampooned the situation in a mock journal titled “The Diary of Carla B.” In it, the diarist wondered if her husband “cheats” — at karate.

As for the rumors about herself, Bruni told Sky News, “I must say that maybe 99 percent of things that people are saying are wrong . . . But it was always like that, even before my marriage.” With Post Wire Services